The present invention relates to a measuring device with electrodes on porous membrane substrate in which the sample migrates chromatographically; and the method of quantifying material in the sample by using the device.
More specifically, this invention relates to a measuring device with pretreatment bands in the lower part of porous membrane substrate; and electrodes in the upper part of pretreatment bands.
The method of quantifying contains processes as follows: the sample material for measuring is chromatographically migrated in the porous membrane substrate on applying the sample by the lower part of the porous membrane substrate; and then the changes of electric signal (i.e. current, potential, conductivity, etc.) by the material at the electrode is measured to quantify the material.
Recently, the need of quantification of organic/inorganic species in the sample is increasing for the purposes of diagnosing and preventing diseases, adjusting processes in food and industrial chemistry field or analyzing pollutants.
Firstly, measuring the concentration of small amount of organic/inorganic species is carried out by chemical methods; for example, iron salt-sulfuric acid reaction or p-toluene salt-sulfuric acid reaction, which are used in quantifying cholesterol in blood. However, there are demerits in using these methods, because the above reactions are very sensitive to the experimental condition, requires large amounts of sample, and suffers from a severe interference. Thus, other methods such as immunological method using antibody or enzymatic method are often employed these days. These methods are extensively used because of the small amount of the sample, superior selectivity and accuracy, and also the ease of its manipulation.
Since immunological or enzymatic methods cannot give direct results, the concentration measurement is observed with fluorometry, colorimetry, spectrometry and electrochemical method using electrodes.
Among these methods, the chromatographic method using porous membrane substrate (i.e. nitrocellulose papers, filter papers and so on) can separate or remove the interfering material during the migration due to capillary phenomenon by the measuring sample. Additionally, various substrates in which the sample is pretreated are easily fabricated with this method. Therefore, it has been extensively used in various fields such as pregnancy diagnosis kit, cholesterol sensor, and so forth. However, the chromatographic method using porous membrane substrate is not suitable for quantitative analysis, because it is mainly used in qualitative analysis by observing the change of color or tint by the naked eye.
Recently, the method using sensor with electrodes is widely used in analyzing and measuring the material. The method is performed by measuring the changes of the material resulting from immunological or enzymatic reaction electrically through electrodes. This method has merits of superior selectivity and accuracy. But it also has demerits of the inability to pretreat the sample due to the difficulties in employing pretreatment band. In order to quantify the material by electrodes, the sample is adjusted beforehand to be applicable to the electrometer, and then it is applied to electrometer. However, complicated analyzing steps and requirement of skilled personnel remain as the problems of this method.